Thailand cave rescue: Why can't they drill from above, other questions you want answered

The 12 boys and their coach who are trapped in an underground cave in Thailand have riveted attention on efforts to rescue them. Authorities describe the situation as a race against time to avoid death.

As cave experts from around the world converge on Tham Luang Nang Non cave, the inevitable monsoon rains of northern Thailand have made the rescue efforts increasingly grim. A former Thai navy seal diver died during the rescue effort Thursday after running out of oxygen while attempting to deliver air tanks.

USA TODAY, through interviews and research, compiled this list of questions and answers to address why the mission is so difficult:

If rescuers know where the boys are, can't a drill be used to open a hole from above and hoist the boys out?

The spot where the boys and their coach are is about a half-mile down, through mostly solid rock. The mountain terrain above the cave is heavy jungle, with few access roads.

Forrest Wilson, the chief diving officer for the National Cave Rescue Commission and who has 50 years of cave diving experience, including several rescues, said drilling into the cave from above is not impossible. But the maps of the cave are not accurate enough to get a good fix on exactly where to drill.

"It will take a long time to drill through a half a kilometer of cave," Wilson said. "I don't think there's time."

Isn't there a way, using modern technology, that rescuers could get a more accurate fix from above on where the boys are?

Yes, there is. It's called a radio cave locator and it's basically a beacon that transmits a radio wave from within the cave and lets people on the outside know precisely where the beacon – and the trapped people – are located.

It's unclear if authorities in Thailand are using such a beacon — or if it is making any difference to the rescue effort. Since drilling through such heavy rock would take weeks, having a precise location is probably a moot point.

That's a big cave. Why are rescuers so worried about oxygen?

Ventilation from the surface is poor. There's simply not enough air going into the cave space to sustain 12 boys and an adult for a long period of time. Rescue workers are trying to run an oxygen line from the mouth of the cave to the chamber where the trapped people are, but that's about three miles.

The oxygen level in the cave is estimated to be about 15 percent and decreasing (normal oxygen level is about 21 percent.) A low oxygen level means simple tasks like thinking and basic physical exertion become gradually more exhausting.

Can't the water from the cave simply be pumped out?

Not all of it. Heavy industrial pumps are pumping water out of the cave around the clock, and authorities on Friday estimated they have pumped out more than 35 million gallons in the past week. But seeing as how a cave is a huge water repository, the millions of gallons being pumped out amounts to proverbial drops in a bucket.

In about four months, Thailand's dry season would naturally deplete the water in the cave. But rescue workers don't believe that the boys can hold on that long, considering oxygen levels and other concerns.

So, what is the best chance to get the trapped people out?

Find a back entrance to the cave. "A cave as large as the one they're in is bound to have a back entrance," Wilson said. "There would be no problem if they found one. They could put harnesses on the kids and pull them out."

But finding that back cave entrance in such heavy jungle is extremely difficult. The entrance would likely be a simple hole in the ground, commonly called a "chimney" that would hopefully go straight down to a cavern near where the boys are. But the entrance hole for such a chimney would be hard to spot because of the forest. "There are people walking all over that jungle right now trying to find it," Wilson said.

Can't the boys just swim out with the help of expert divers?

Sure, but it is very risky. The boys and their coach have been trapped for nearly two weeks and they are getting weaker. Most do not know how to swim. Authorities, however, are increasingly thinking that this may be the best course at this point, since heavy rain is expected Sunday. Thailand's Navy Seal commander said Friday that such an operation would be a daring and risky operation, but that it may be the only chance.

"That would be a heck of a job," Wilson said. "The kids are not in good shape to be swimming out. It's a five-hour swim job. It's scary."

How often do people get trapped like this in caves in the U.S. and other countries? Is this rescue more difficult than others?

The Thai rescue operation is probably more treacherous than others because of the sheer size of the cave, the oncoming monsoon season, and the isolated area. Wilson said that in his many years as a diver, "I've never done one as extensive" as the Thai attempted rescue.

In the late 1970s, Wilson and others rescued a group of college students in Kentucky under somewhat similar circumstances. The students went into a dry cave that, after a heavy rain, became filled with enough water to block their way out. Eventually, all of the students were rescued after divers kept them well stocked with blankets and food.

Is there any way to prevent these kinds of cave incidents from happening?

One of the best defenses that cave explorers can be armed with is knowledge of the upcoming weather: If it looks like it may rain, it is not a good idea to go deep into a cave.

But preventing cave exploration, even on rainy days, is unlikely.

"That would be like telling people, 'Don't drink and drive,'" Wilson said. "People are going to do it, even if it's risky."

WSBTV